In recent years, semiconductor devices with package types such as SON (Small Outline Non-leaded Packages) and QFN (Quad Flat Non-Leaded Packages) have been widely manufactured. An example of a QFN semiconductor device is shown in FIG. 77 in cross-sectional view (e.g., see Patent Document 1). The semiconductor device 90 shown in FIG. 77 is provided with a resin case 91, a base lead 92, a semiconductor chip 93, lead terminals 94, and connection wires 95. The semiconductor chip 93 is fixed to the base lead 92, and is connected to the lead terminals 94 via the connection wires 95. Semiconductor devices such as the semiconductor device 90 are manufactured using a lead frame. A lead frame is manufactured by forming a metal plate having a thickness of about 0.2 mm into a desired pattern by punching with a precision press or etching.
When manufacturing the semiconductor device 90 using a lead frame, the semiconductor chip 93 is placed on the base lead 92, and the semiconductor chip 93 and the lead terminals 94 are connected with the connection wires 95, before covering the lead frame with the resin case 91. Thereafter, unnecessary portions of the lead frame are cut off and removed.
There are calls to downsize the semiconductor device 90 following the downsizing of various electronic devices. One conceivable method of downsizing is to reduce the dimensions of the semiconductor device 90 in the thickness direction. The thickness of the base lead 92 and the lead terminals 94 which are formed from a metal plate is not a favorable element in making the semiconductor device 90 thinner. Manufacturing semiconductor devices in a package form without using a lead frame has thus been proposed. For example, a technique that involves forming terminals by plating on a metal base, and subsequently removing the base by etching is known (e.g., see Patent Document 1).
However, in the case where terminals are formed by plating as described above, without using a lead frame, the thickness of the terminals will be about 20 μm, and the terminals could possibly be more likely to separate from the resin case. In terms of manufacturing semiconductor devices without using a lead frame, securing the pullout strength of the terminals is an issue.
Conventionally, various methods for manufacturing semiconductor devices have been conceived besides the abovementioned examples. For example, in a method disclosed in Patent Document 2, first an external electrode pad part is formed on a metal plate having high flatness. Next, the metal plate and the external electrode pad part are covered with an insulating resin thin film layer. Next, after forming an opening in the insulating resin thin film layer, a metal thin film interconnect part is formed in the opening. Next, the metal thin film interconnect part is covered with an insulating resin thin film layer. A plurality of metal thin film interconnect parts are stacked by repeating processes such as the above. Next, a multilayer interconnect substrate is formed by removing the metal plate by etching. A semiconductor chip is mounted to the multilayer interconnect substrate, and the metal thin film interconnect parts in the multilayer interconnect substrate are thus electrically connected to electrodes of the semiconductor chip.
In a method for manufacturing a semiconductor device such as this, photolithography is performed to etch the metal film formed on the metal plate when forming the metal thin film interconnect parts. Since the metal thin film interconnect parts are formed in sequence on the metal plate, the photolithography is also performed in sequence. To perform photolithography, tasks such as forming a photomask and preparing an exposure machine are necessary, requiring time and effort.